Cancer Stem Cell Discovery Could Hold Key To First Real Cure For The Disease

In some cancers, doctors find that tumors shrink with treatment, yet only briefly, and then come back with a vengeance. Now, recent studies on three different types of tumors suggest that cancer stem cells are resistant to chemotherapy and radiotherapy and may explain why cancer becomes resistant to treatment.

A team of independent researchers came to the realization while studying tumors of the brain, intestines and skin in mice. Properties of so-called cancer stem cells that the researchers found could be further investigated and hopefully lead to new strategies in killing them off, said Luis F. Parada, a molecular geneticist at the University of Texas Southwestern Medical Center in Dallas and senior author of the brain cancer study published on Wednesday.

“If these cells are indeed the cells that fuel tumor growth then maybe you can target these cells,” Professor Cedric Blanpain of the Free University of Brussels, who led the skin cancer study, told Pallab Ghosh at BBC News.

In the three separate cancer studies, the researchers have shown the growth and life of a tumor to be dependent on one small group of stem cells, they call “mother cells.” These cells are thought to fuel the disease´s spread around the body — the most common reason patients die from cancer.

Scientists had long believed certain cells were responsible for cancers coming back after treatment. But until now, nobody had proved them to exist in tumors.

The breakthrough, reported in the journals Nature and Science, brings researchers hope that they can finally find a cure for a disease that kills more than 150,000 people each year in the UK alone.

Scientists liken killing cancer stem cells to killing dandelions by pulling them out by the roots, rather than just removing the head. By combining a drug that attacks the stem cells with current treatments for cancer, they say a cure could likely occur.

But that could be easier said than done. Since the newly-discovered stem cells are very similar to healthy stem cells responsible for growing and renewing tissue in the body, any therapy targeting cancer stem cells could also destroy healthy cells. Researchers would need to deeply examine both types of cells to tease apart an differences that could be targeted in one cell and not the other.

Despite the roadblocks ahead, the confirmation that these cells even exist is important and groundbreaking for future cancer research, said Professor Hugo Snippert of the University Medical Centre in Utrecht, who led the study into intestinal tumors.

“Many argued that these cells did not exist. But we have shown for the first time there is such a thing as a cancer stem cell and that tumors are maintained by them,” he said.

The results shown here, by three separate studies, “really should seal the deal,” cancer biologist Owen Witte, director of the Broad Stem Cell Research Center at UCLA, told the Los Angeles Times. “People can stop arguing. Now they can say, ℠OK, the cells are here. We now need to know how to treat them.´”

All three studies used molecular tricks that allowed the scientists to mark certain tumor cells with bright colors. When these marked cells were divided, all of the daughter cells were similarly colored. This allowed researchers to see if old cells in the tumor continued to fuel growth or if only a subset of cells were responsible.

While all three teams used different approaches and different forms of cancer, they all found the subset of cells were solely responsible for re-growth.

There are many barriers that will need to be addressed, according to MIT cancer researcher Robert Weinberg, who was not involved in any of the new studies. But, while barriers need to be overcome before the new findings can be implemented in cancer treatment, it is obvious now that doctors can´t just go after rapidly dividing cells to effectively fight cancer.

Traditional cancer medications and treatments only kill rapidly dividing cells, and scientists do not know enough about cancer stem cells yet to target them. However, biotech companies and academics are working the problem out.

John E. Dick, senior scientist at Toronto’s Princess Margaret Cancer Center, whose 1990s cancer research provided early evidence for stem cells in leukemia, said continuing on the findings will be complicated, and that complexity will make the prospect of devising new therapies seem daunting. But, he added, it opens up a whole new menu of strategies that scientists can try.